Guess I wouldn't be sure what to make of this then (For a Benelli Super Nova)? My calipers pull a max of 0.6680", so that doesn't help, although it does NOT have 3 rings (visible) in the bore, just the restriction taper line.
So, here's the fun part:
Clearly labeled with the "hevi-shot dead coyote" logo at the end. BUT, it does not have the 3 rings internally that the Hevi-shot model is supposed to have, which would suggest that it's the NOT the Hevi-Shot model, but simply the Carlson's model...
BUT, it's pretty clearly labeled "Carlson's Dead Coyote Choke", not simply the "Carlson's Coyote Choke" like you'd suggested...
They also used to cut them at 0.680" or 0.660", with no distinction between the two, so if you got one, and wanted the other, you mailed it to Carlson's for an exchange...
WTH's going on? Simple answer by my best guess is that Hevi-Shot and Carlon's had a deal to make Hevi-shot chokes labeled as such, corresponding to the Dead Coyote product line. At some point there was a decision to add the "stripper rings" to the bore, which isn't compatible with all shot cups/wads (black cloud, federal, etc), so they simply made two different models. Since the one with rings wouldn't be specifically designed for the hevi-shot, and meant for OTHER shot, I'm sure Hevi-shot didn't really want their "dead coyote" name getting used on it, so now we have TWO NEW chokes made by the same company for essentially the same purpose, but with a concession for which shot cup/wad you're using.
Personally, I don't care who's name is on it. It patterns great, was pretty cheap, and it puts fur in the dirt. If/when I decide to get another one for my wife's shotty, I'm not going to be too picky whether it has 0.665" or 0.664" or whether it has rings or not. If it does have rings, I'll pattern it and make sure it works as well as this one, if so, it'll get the nod.